The present invention is applicable to video systems for hospitals, schools, condominiums as well as hotels and other systems having a large number of independently controlled televisions or video monitors. For the purposes of illustrating and explaining the invention, however, the prior art and the preferred embodiment of the invention will be described in the context of a video system for a hotel.
Hotels often provide video program services beyond those available on publicly available television channels and publicly accessible cable television. The main types of prior art systems are video tape rental systems, fixed schedule movie systems that broadcast pay-per-view programming on predefined channels on a fixed schedule as well as free programming on other channels, and on-demand movie systems that broadcast free programming on one set of channels and use other channels to transmit pay-per-view programming to users upon request by the users.
The present invention provides a number of improvements on the on-demand type of cable television systems disclosed in U.S. Pat. No. 4,947,244, issued Aug. 7, 1990, entitled "Video Selection and Distribution System."
In particular, the present invention is designed to work in settings where the cable television system must carry television signals in two or more formats. For instance, in some places such as Singapore, some television channels are broadcast in PAL format while other television channels are broadcast in NTSC format. In other places television signals are broadcast both in SECAM and PAL formats. Furthermore, movies and other programming from various sources are recorded on cassettes in a variety of video signal formats, and each such cassette must be played using a video cassette player that outputs television signals in the corresponding signal format.
Another problem addressed by the present invention is that in some situations it is unacceptable to place a television converter box on top of the user's television set or anywhere else in the user's visual field, and yet the user must still be able to make program or channel selections using a remote control device pointed at the user's television. Furthermore, in these situations it is generally not possible (or not economically feasible) to modify the control circuitry in the television sets due to cost considerations and the age of the television sets. As a result, the cable converter box must be hidden from the user's view and cannot be connected to the television set's internal controller. Thus the only connection between the cable converter box and the television is a cable connected to the antenna or cable input port on the back of the television.
This presents two sets of problems: (A) the controller cannot turn the television on and off and cannot set the television to a particular channel, and (B) the controller cannot obtain signals directly from the television's controller for determining whether the television is on and similarly cannot obtain signals directly from the television's controller for determining the channel to which the television is tuned. Thus, unless some countervailing measures are taken, random use of the remote control wand while the user's television is off might result in the selection and playing of a pay-per-movie and a subsequent charge to the user despite the fact that the user's television is off.